Can you revise your question so I can understand what you want to achieve? Right now, I am not sure who calls whom and what phone is supposed to be ringing?

Hi Phong, thank you for getting back to me so quickly.

This is one-way only: dialing out. We want our employees to log in to our system and be presented with a list of scheduled calls for them (obviously our system would handle all of that). When they click 'call', it would automatically choose a free RingCentral line and dial out on that line (with recording).

Essentially, we want our system to authenticate with RingCentral and do all the heavy lifting so that the user can just click 'call' and not worry about logging in to a RingCentral account or anything like that.

I am not sure if this helps your use case, but here is what I can suggest you to explore. I assumed that this is a private app that serves only your own company.

Use the Ring Out API to place a call between 2 numbers (e.g. your employee's number and a customer's number). You can use the Presence API to to detect free "employee".